Mabch 9, 1906.] 



SCIENCE. 



363 



and problems at hand, such as the behavior 

 of bodies at various moderate temperatures, 

 have received more study than their in- 

 trinsic importance requires, while remoter 

 objects such as the heavenly bodies, and 

 very high and low temperatures have not 

 received the attention which they deserve. 

 Doubtless the same fact holds in the biolog- 

 ical sciences, including physiology and 

 medicine. Experiments upon the physi- 

 ological action of drugs have probably re- 

 ceived, especially in the past, relatively too 

 much attention, because of the ease with 

 which they could be carried out ; while the 

 more difficult and more costly experiments, 

 for example those required to determine 

 the purity of large bodies of water, such as 

 rivers and lakes, or those upon the purifica- 

 tion of sewage, have until recently received 

 but little attention. 



There is danger, moreover, that in the 

 instinctive recognition of the difficulties of 

 laboratory experiments upon large and dif- 

 ficult problems, investigators shall turn 

 aside from the careful study and verifica- 

 tion of the data and results of another class 

 of experiments which, for the sake of differ- 

 entiation, we may call natural rather than 

 artificial experiments, and which in every- 

 day language are described as experience. 

 It is, for example, obviously unwise to re- 

 gret our inability to test by the methods of 

 ordinary artificial experiment the effects of 

 polluted drinking water upon large com- 

 mimities, when there are frequently being 

 exhibited, all about us, by such communi- 

 ties, natural experiments on a grand scale, 

 the conditions of which can often be accu- 

 rately determined, even after the fact, and 

 the results of which are as capable of veri- 

 fication as are those of artificial experi- 

 ments prearranged to answer specific ques- 

 tions. 



When, in 1893, the city of Lawrence, 

 Mass.— long in the habit of drinking the 

 unpurified water of the polluted Merrimac 



River, into which only nine miles above the 

 intake of the Lawrence waterworks the raw 

 sewage of the city of Lowell was poured — 

 set up between that water and its citizens 

 a barrier of defense (a sand filter) per- 

 meable by water but impermeable by dis- 

 ease germs, an experiment was undertaken 

 under conditions quite as clear and as fa- 

 vorable as those under which many labora- 

 tory experiments are conducted. The data 

 at hand concerning this experiment— con- 

 cerning its cause, inception, conduct and 

 consequences, were such as to enable those 

 having the opportunity to study it to reach 

 results, and to draw conclusions, of high 

 accuracy, and even to predict with confi- 

 dence the consequences of similar experi- 

 ments elsewhere. This experience of a 

 modern American municipality was also an 

 experiment in the narrower sense— al- 

 though not a laboratory experiment; for it 

 was made artificially, and by prearrange- 

 ment, in order to solve a specific problem, 

 namely, to get rid of typhoid fever in a 

 community in which that disease had long 

 been, in the old phraseology, 'endemic' 



One experiment often leads to another, 

 and so also an experience often leads to an 

 experiment. Years before, in 1872, acting 

 under the best engineering and scientific 

 advice of the time, the city of Lawrence 

 had introduced for the benefit of its citi- 

 zens a public water-supply drawn directly 

 from the Merrimac Eiver nine miles below 

 the mouths of the sewers of Lowell, as al- 

 ready stated above. In doing this there 

 was no thought of making any scientific or 

 sanitary experiment, but only of supply- 

 ing the city with water for fire purposes 

 and domestic convenience. Unwittingly, 

 however, an important experiment was 

 really being made by that municipality. 

 As surely as if by premeditation and pre- 

 arrangement a trial was being made, day 

 by day, and year by year, of the effect upon 

 the public health of the city of the use of a 



